Firefox stopped responding whenever I attempted to access a site. I could verify network connectivity to various sites with ping, but if I attempted to access a URL in the Firefox browser on my MacBook Pro running OS X El Capitan, Firefox (version 45.7.0) would not display any webpage. I've had this problem in the past; when it occurred, I would quit Firefox, sometimes using Force Quit Applications, which is available by clicking on the Apple icon at the top, left-hand corner of the screen and then selecting Force Quit and then selecting Firefox from the Force Quit Applications list of running applications and then clicking on the Force Quit button. When I did that today, I saw the message below as usual:
I clicked on Force Quit, but that seemed to have no effect. I closed and reopened Force Quit Applications and went through the same process numerous times, but no matter how many times I repeated the process, Firefox remained in the list of running applications that it showed.
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